Re: xvifX.Y vs sysctl_create() returning 22 (EINVAL)

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Tue, Jan 11, 2011 at 02:52:17AM +0100, Jean-Yves Migeon wrote:
> Hi list,
> 
> Due to the syntax currently used for xvif(4) interfaces, their creation
> during a domU start results in the following messages logged:
> 
> Jan 10 00:02:26 paris /netbsd: xvif108.0: could not attach sysctl nodes
> Jan 10 00:02:57 paris /netbsd: sysctl_createv: sysctl_create(xvif108.0)
> returned 22
> 
> Consequently, the interface is not visible under net.interfaces in
> sysctl(7).
> 
> Fixing this issue would need to get rid of the "." from the interface
> name, and replace it with a correct char acceptable for the MIB.
> 
> Sadly, we cannot make such a "radical" change without breaking current
> scripts used for vif initialization, like etc/xen/scripts/vif-ip or
> vif-bridge (the pattern is hardcoded within).
> 
> I would like to propose the following changes, so to ease the transition
> a bit:
> 
> - similar to what is done for XenSource's Linux, create a "vifname" node
> inside XenStore, which contains the vifnames (doh!) for the domain just
> created. In our case, for dom0, that would be "xvifX-Y", or anything
> that avoid using dots in the name (X being domU ID and Y the frontend
> interface ID).
> 
> - modify the vif-ip and vif-bridge scripts: introduce a
> "xenstore_read_default" function, like done for Linux:
> 
> # xenstore_read_default <path> <default>
> #
> # Read the given path, returning the value there or the given default
> # if the path is not present.
> #
> xenstore_read_default() {
>   xenstore-read "$1" 2>/dev/null || echo "$2"
> }
> 
> - use it to query the "vifname" keys; obviously, keep the "xvifX.Y" as
> default syntax.
> 
> - wait for an arbitrary amount of time (TBD), so that Xen scripts get
> eventually replaced by their newer versions.
> 
> - finally, modify the syntax in kernel. Consequence: vifname will change
> its syntax within xenstore for each new domU, and the newer scripts will
> take that into account "automagically."
> 
> Opinions?

This looks good. The "amount of time" to wait is probably one quartely pkgsrc
release. Too bad 2010Q4 has just been branched ...

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--